1. Field of the Invention
The present invention relates to an uninterruptible power supply apparatus that is used as a measure against power-failure for computer equipments such as disk array apparatuses, and more particularly to a technology that is effective when applied to an uninterruptible power supply that is connected to a computer equipment having two systems of power supply line inputs.
2. Related Background Art
A conventional uninterruptible power supply (UPS) apparatus typically has a plurality of AC power supply outputs, but only one system of AC power supply input for the UPS.
A computer equipment such as a disk array apparatus typically has two systems of AC power supply line inputs in order to prevent a system halt due to a trouble occurring at one point, in other words, such a computer equipment can cope with a power failure or a power supply trouble in only one of the systems.
When a UPS is connected to a computer equipment such as a disk array apparatus having two systems of AC power supply line inputs, one of the following three methods is conventionally used to connect the UPS to the two systems of AC power supply line inputs of the computer equipment:
{circle around (1)} The UPS is connected to only one of the two systems of AC power supply line inputs, and the other one of the AC power supply line inputs is not connected to the UPS, but directly connected to the AC power supply line.
{circle around (2)} One AC power supply output of the UPS is connected to the two systems of AC power supply line inputs, and the AC power supply line redundancy function is not used.
{circle around (3)} An additional UPS is prepared (i.e., two UPSs are prepared), and the two systems of AC power supply line inputs are connected to the two UPSs, respectively.
In addition, as an uninterruptible power supply apparatus to be connected to an apparatus having two systems of AC power supply line inputs, an all-time inverter type static uninterruptible power supply apparatus is known. This uninterruptible power supply apparatus is equipped with constant-voltage constant-frequency power supply units for two systems, and one system storage battery for the constant-voltage constant-frequency power supply units for two systems.
However, when a UPS is connected to a computer equipment having two systems of AC power supply line inputs by the conventional methods {circle around (1)}, {circle around (2)} and {circle around (3)} described above, the following problems arise, respectively:
{circle around (1)} Because the UPS is connected to only one of the two systems of AC power supply line inputs, power failure that occurs in the two AC power supply lines would cause power failure in one of the two systems of AC power supply line inputs that is directly connected to one of the AC power supply lines. Also, a shutdown process may not be normally performed, when only one of the AC power supply lines that is connected to the UPS has a power failure, the battery of the UPS is used up and the output of the UPS is shut off, and then later the other AC power supply line has a power failure,.
Moreover, if there is a power supply link function between the UPS and the computer equipment connected to the UPS, a half of the power supply link function does not work.
{circle around (2)} A part of the AC power supply line redundancy function cannot be used, and therefore the AC power supply line redundancy function would not provide a strong measure against troubles in the power supply system.
{circle around (3)} Two UPSs are required, such that the system becomes expensive.
Also, in the case of the all-time inverter type static uninterruptible power supply apparatus, since each of the constant-voltage constant-frequency power supply units is equipped with a rectifying and charging circuit and a power inverter circuit, the system becomes expensive like the case where two UPSs are prepared.